Gasification processes are widely used to convert solid or slurried feedstocks such as coal, petroleum coke and petroleum residue into synthesis gas. Synthesis gas is predominantly composed of hydrogen gas (H2) and carbon monoxide (CO), and is utilized both as fuel for the production of electricity, as well as a feedstock for producing chemicals such as hydrogen, methanol, ammonia, synthetic/substitute natural gas or synthetic transportation oil. Three basic types of system and processes have been developed for the gasification of carbonaceous materials. They are: (1) fixed-bed gasification, (2) fluidized-bed gasification, and (3) suspension or entrainment gasification, Embodiments herein relate to the third type of system and, more particularly, embodiments presented herein relate to a two-stage entrained gasification system and process for gasifying carbonaceous materials.
The possibilities presented by the two-stage gasifier design can be exploited by maximizing the slurry feed rate to the lower temperature second stage, thereby utilizing the heat generated in the first stage gasifier to evaporate water from the slurry. The char and unconverted carbon exiting the second stage gasifier are then separated and recycled back to the first stage gasifier in dry form, thus minimizing the amount of oxygen required in the higher temperature first stage and maximizing the conversion efficiency of the gasifier.